[bouncer]

Pretty simple.
If a player has custom flag O, he will never get flashed regardless who throws the flash nade.

[thetwistedpanda]

You can modify the Anti Team Flash in my signature to meet your needs rather easily >.<.

[bouncer]

I cant seem to find out what the cvar is to set the custom flag required to be immune to flashes in your plugin?

[thetwistedpanda]

Use ReadFlagString() and GetUserFlagBits() (see http://docs.sourcemod.net/api/ for information on how to use them) and you should be able to figure it out.